(1 + ε)-Approximation for Facility Location in Data Streams∗
Bibliographic record
Abstract
We consider the Euclidean facility location problem with uni-form opening cost. In this problem, we are given a set of n points P ⊆ R2 and an opening cost f ∈ R+, and we want to find a set of facilities F ⊆ R2 that minimizes f · |F |+ p∈P min q∈F d(p, q), where d(p, q) is the Euclidean distance between p and q. We obtain two main results: • A (1 + ε)-approximation algorithm with running time O(n log2 n log log n) for constant ε, • The first (1 + ε)-approximation algorithm for the cost of the facility location problem for dynamic geometric data streams, i.e., when the stream consists of insert and delete operations of points from a discrete space {1,...,∆}2. The streaming algorithm uses log ∆ ε)O(1) space. Our PTAS is significantly faster than any previously known (1 + ε)-approximation algorithm for the problem, and is also relatively simple. Our algorithm for dynamic geometric data streams is the first (1 + ε)-approximation algorithm for the cost of the facility location problem with polylogarithmic space, and it resolves an open problem in the streaming area. Both algorithms are based on a novel and simple decompo-sition of an input point set P into small subsets Pi, such that: • the cost of solving the facility location problem for each Pi is small (which means that one needs to open only a small, polylogarithmic number of facilities), • ∑i OPT(Pi) ≤ (1 + ε) ·OPT(P), where for a point set P, OPT(P) denotes the cost of an optimal solution for P. ∗Research partially supported by the EU within the 7th Framework
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.003 | 0.012 |
| Meta-epidemiology (narrow) | 0.003 | 0.001 |
| Meta-epidemiology (broad) | 0.003 | 0.002 |
| Bibliometrics | 0.001 | 0.004 |
| Science and technology studies | 0.001 | 0.001 |
| Scholarly communication | 0.003 | 0.008 |
| Open science | 0.005 | 0.003 |
| Research integrity | 0.003 | 0.004 |
| Insufficient payload (model declined to judge) | 0.007 | 0.002 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".